Circuit interruption device and method of assembly

ABSTRACT

A circuit interruption device includes a conductive element configured to be coupled to a circuit, a contact arm configured to move with respect to the conductive element between a first position and a second position, and a biasing element configured to apply a biasing force on the contact arm to maintain contact between the contact arm and the conductive element when the contact arm is in the first position, wherein the contact arm is configured such that a current flow through the contact arm causes an electromagnetic repulsive force to act on the contact arm in a second direction that is opposite the first direction.

BACKGROUND OF THE INVENTION

The embodiments described herein relate generally to circuit protectiondevices and, more particularly, to circuit interruption devices.

At least some known circuit protection devices include a stationarycontact arm and one or more movable contact arms. During normaloperations, the stationary and movable contact arms are maintained incontact to enable current to flow through the circuit protection device.However, when a current condition, such as a short circuit or currentspike, is detected, the circuit protection device causes the movablecontact arm to move away from the stationary contact arm to preventcurrent from flowing therebetween. Moreover, at least some known movablecontact arms are shaped to guide current flow from the movable contactarm into the stationary contact arm. For example, at least some knownmovable contact arms are shaped such that a current path between themovable contact arm and the stationary contact arm is a substantiallystraight path.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a circuit interruption device includes a conductiveelement configured to be coupled to a circuit, a contact arm configuredto move with respect to the conductive element between a first positionand a second position, and a biasing element configured to apply abiasing force on the contact arm to maintain contact between the contactarm and the conductive element when the contact arm is in the firstposition, wherein the contact arm is configured such that a current flowthrough the contact arm causes an electromagnetic repulsive force to acton the contact arm in a second direction that is opposite the firstdirection.

In another aspect, a trip mechanism is provided for use with a circuitbreaker, wherein the trip mechanism includes a conductive elementconfigured to be coupled to a circuit, and a contact arm configured tomove with respect to the conductive element between a first position anda second position. The contact arm is configured such that a currentflow through the contact arm causes an electromagnetic repulsive forceto act on the contact arm in the second direction.

In another aspect, a method of assembling a circuit breaker includescoupling a conductive element to a circuit, positioning a contact armwith respect to the conductive element, and coupling a biasing elementto the contact arm. The biasing element is configured to apply a biasingforce on the contact arm in a first direction to maintain contactbetween the contact arm and the conductive element when the contact armis in the first position. The contact arm is configured such that acurrent flow through the contact arm causes an electromagnetic repulsiveforce to act on the contact arm in a second direction that is oppositethe first direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of an exemplary circuit interruption device.

FIG. 2 is an exploded view of an exemplary trip mechanism that may beused with the circuit interruption device shown in FIG. 1.

FIG. 3 is a cross-sectional view of the trip mechanism shown in FIG. 2.

FIG. 4 is a partial side view of a portion of the trip mechanism shownin FIG. 2.

FIG. 5 is a partial perspective view of a portion of the trip mechanismshown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of apparatus for use with circuit interruptiondevices and methods of assembling circuit interruption devices aredescribed herein. These embodiments facilitate enhancing circuitinterruption device performance by changing a direction of current flow.Changing the direction of current flow enables faster response toabnormal current conditions and faster mitigation of electrical arcscaused by separation of the electrical contacts within the circuitinterruption device. For example, the response to abnormal currentconditions is enhanced by providing a greater repulsive force betweenthe electrical contacts to overcome a biasing force that maintainscontact between the electrical contacts. This reduces the clearing timefor the circuit interruption device to fully open or trip. Moreover, anelectrical arc is extinguished faster due to an additional propulsiveforce that causes the energy of the electrical arc to move into an arcchute comprised of a plurality of arc mitigation plates.

FIG. 1 is an exploded view of an exemplary circuit interruption device100, such as a circuit breaker. In an exemplary embodiment, circuitinterruption device 100 includes a base 102 and a cover 104 that couplesto base 102. For example, base 102 includes a top edge 106 and cover 104includes a bottom edge 108 sized to couple to top edge 106 and form ahousing. Circuit interruption device 100 also includes one or more tripmechanisms 200 and a relay 110. Although FIG. 1 shows three tripmechanisms 200 within circuit interruption device 100, it should beunderstood that more or fewer trip mechanisms 200 may be used withcircuit interruption device 100. In an exemplary embodiment, relay 110detects an abnormal current condition, such as an overcurrent or shortcircuit condition, through a circuit (not shown) that connects a powersource to a load. Specifically, a portion of the circuit is coupled toone or more input terminals 112 that each corresponds to a respectivetrip mechanism 200. Moreover, a portion of the circuit is coupled to oneor more output terminals 114 that each corresponds to a respective tripmechanism 200. For example, in one embodiment, the circuit includes aplurality of conductors, such as a line conductor, a neutral conductor,and a ground conductor, each of which is coupled to a respective inputterminal 112 on the line side of circuit interruption device 100 and toa respective output terminal 114 on the load side of circuitinterruption device 100. In an exemplary embodiment, circuitinterruption device 100 also includes a means of manually openingelectrical contacts within each trip mechanism 200. For example, asshown in FIG. 1 circuit interruption device 100 includes an openingmechanism 116 and a handle 118. Opening mechanism 116 is coupled to oneor more of trip mechanisms 200 and is oriented to engage handle 118 andreceive a user input. Handle 118 extends through a top surface 120 ofcover 104 to be externally accessible to a user.

FIGS. 2 and 3 are views of an exemplary trip mechanism 200 for use withcircuit interruption device 100 (shown in FIG. 1). Specifically, FIG. 2is an exploded view of trip mechanism 200 and FIG. 3 is across-sectional view of trip mechanism 200. As shown in FIG. 2, tripmechanism 200 includes a housing having a first housing portion 202 anda second housing portion 204. Housing portions 202 and 204 include afirst inner edge 206 and a second inner edge 208, respectively, andhousing portions 202 and 204 are coupled together along inner edges 206and 208. Input terminal 112 extends through a front surface 210 of firsthousing portion 202. Similarly, output terminal 114 extends through arear surface 212 of first housing portion 202.

In an exemplary embodiment, trip mechanism 200 includes a contact arm214 coupled to a biasing element 216, such as a spring. Trip mechanism200 also includes a conductive element 218, such as a line strap.Biasing element 216 is positioned within a biasing element enclosure 220and causes contact arm 214 to rotate about a shaft 222 between a firstposition, such as a closed position, and a second position, such as anopen position. As described in detail below, a portion of contact arm214 contacts a portion of conductive element 218 when contact arm 214 isin the first position to enable current to flow from contact arm 214 toconductive element 218. Moreover, biasing element 216 applies a biasingforce to contact arm 214 in a first direction (not shown in FIGS. 2 and3) to maintain contact arm 214 in the first position. When contact arm214 is in the second position, contact arm 214 and conductive element218 are not in contact, thereby preventing current from flowing throughcontact arm 214 to conductive element 218.

When an abnormal current condition occurs, such as an overcurrent,contact arm 214 separates from conductive element 218 due to anelectromagnetic repulsive force generated in a second direction (notshown in FIGS. 2 and 3) that is opposite the first direction. Therepulsive force is generated between contact arm 214 and conductiveelement 218 based on a current flow through contact arm 214, as setforth below, such that when the current flow causes the repulsive forceto exceed the biasing force, contact arm 214 separates from conductiveelement 218. The electromagnetic repulsive force between contact arm 214and conductive element 218 also generates an electric arc. In anexemplary embodiment, trip mechanism 200 also includes a plurality ofarc mitigation plates 224 that are positioned within an arc enclosure226 to form an arc chute. Arc mitigation plates 224 and arc enclosure226 are oriented within first and second housing portions 202 and 204such that the energy of the arc is absorbed and/or dissipated by arcmitigation plates 224.

FIGS. 4 and 5 are partial views of a portion of trip mechanism 200.Specifically, FIG. 4 is a partial side view of a portion of tripmechanism 200, and FIG. 5 is a partial perspective view of a portion oftrip mechanism 200. In an exemplary embodiment, conductive element 218includes a first end 228 and an opposite second end 230. A firstelectrical contact 232 is provided along a portion of a top surface 234of conductive element 218 at first end 228. Output terminal 114 isprovided at second end 230.

Moreover, in an exemplary embodiment, contact arm 214 includes a firstend 236 and an opposite second end 238. First end 236 is coupled toinput terminal 112 (shown in FIGS. 1-3). A second electrical contact 240is provided at second end 238. Contact arm 214 includes a first portion,such as a body portion 242, extending from first end 236 towards secondend 238. Contact arm 214 also includes a second portion, such as a headportion 244, at second end 238. Second electrical contact 240 isprovided along a bottom surface 246 of head portion 244 to enableelectrical contact between contact arm 214 and conductive element 218.Moreover, head portion 244 facilitates causing current flowing throughcontact arm 214 to change direction within head portion 244 and prior toflowing to conductive element 218. Furthermore, contact arm 214 includesa third portion, such as a neck portion 248, which is provided betweenbody portion 242 and head portion 244. In one embodiment, neck portion248 defines a notch 250. In one embodiment, notch 250 is formed byremoving material from neck portion 248. In another embodiment, notch250 is composed of an insulating material (not shown) and the remainderof neck portion 248 is composed of a conductive material. In anexemplary embodiment, neck portion 248 is formed to facilitate causing acurrent flow through head portion 244 to change direction, which cancause contact arm 214 to separate from conductive element 218 when theamplitude of the current flow is greater than or equal to a thresholdvalue.

In an exemplary embodiment, contact arm 214 and conductive element 218define an electrical path 252 for current. Electrical path 252 includesa first portion 254 in which the current flows through body portion 242and neck portion 248. Electrical path 252 also includes a second portion256 in which the current changes direction within head portion 244.Electrical path 252 also includes a third portion 258 in which thecurrent again changes direction. Specifically, the current flows throughsecond electrical contact 240 and into first electrical contact 232,where the direction of current flow changes in order to generate therepulsive force.

For example, the changes in direction of the current flow generate anelectromagnetic repulsive force between first and second electricalcontacts 232 and 240. In an exemplary embodiment, the biasing force isapplied in a first direction 260, and when the current is below athreshold level, the biasing force maintains contact between contact arm214 and conductive element 218. However, when the current is greaterthan or equal to the threshold level, the repulsive force overcomes thebiasing force. Specifically, the changes in direction of the currentflow generates the repulsive force in a second direction 262 that issubstantially opposite first direction 260, and that has an amplitude insecond direction 262 that is greater than an amplitude of the biasingforce in first direction 260. Accordingly, when the repulsive force insecond direction 262 is greater than the biasing force in firstdirection 260, contact arm 214 moves in second direction 262 to breakelectrical contact with conductive element 218. For example, a firstcomponent of the repulsive force substantially occurs in seconddirection 262 that is opposite first direction 260, and a secondcomponent of the repulsive force substantially occurs in a thirddirection 264 that is substantially orthogonal to first direction 260and second direction 262. When the amplitude or level of the current isgreater than a threshold amplitude or level, the first component of therepulsive force becomes greater than the biasing force applied tocontact arm 214 by biasing mechanism 216 (shown in FIG. 3). The firstcomponent of the repulsive force causes contact arm 214 to separate fromconductive element 218, thereby preventing current from flowing throughinto conductive element 218. More specifically, the first component ofthe repulsive force causes second electrical contact 240 to move insecond direction 262 to separate from first electrical contact 232.Moreover, the first component of the repulsive force causes formation ofan electrical arc between first and second electrical contacts 232 and240. The second component of the repulsive force propels the arc inthird direction 264 towards the arc chute where the energy of the arc isdissipated by arc mitigation plates 224.

A method of assembling circuit interruption device 100, such as acircuit breaker, includes coupling conductive element 218 to a circuit,and positioning contact arm 214 with respect to conductive element 218.In an exemplary embodiment, contact arm 214 moves with respect toconductive element 218 between a first position and a second position.The method also includes positioning at least one arc mitigation plate224 above at least a portion of conductive element 218 such that arcmitigation plate 224 extinguishes an arc created by a separation ofcontact arm 214 from conductive element 218 when contact arm 214 movesfrom the first position to the second position.

The method further includes providing contact arm 214, including bodyportion 242, head portion 244, and neck portion 248 positioned betweenbody portion 242 and head portion 244. Head portion 244 is configured tofacilitate changing the direction of current flow through head portion244 to cause an electromagnetic force to act on contact arm 214 insecond direction 262. In some embodiments, when contact arm 214 is inthe first position, electrical path 252 is defined. Electrical path 252includes first portion 254 in which current flows through body portion242 and neck portion 248, and second portion 256 in which the currentchanges direction. Electrical path 252 also includes third portion 258in which the current flows into conductive element 218 and then changesto generate the repulsive force.

Moreover, in some embodiments, the method of assembly also includescoupling biasing element 216 to contact arm 214. Biasing element 216applies a biasing force on contact arm 214 in first direction 260 tomaintain contact between contact arm 214 and conductive element 218 whencontact arm 214 is in the first position.

Exemplary embodiments of apparatus and methods of assembling apparatusfor use in circuit protection are described above in detail. Theapparatus and methods are not limited to the specific embodimentsdescribed herein but, rather, operations of the methods and/orcomponents of the apparatus may be utilized independently and separatelyfrom other operations and/or components described herein. Further, thedescribed operations and/or components may also be defined in, or usedin combination with, other systems, methods, and/or apparatus, and arenot limited to practice with only the systems, methods, and storagemedia as described herein.

Although the present invention is described in connection with anexemplary electrical equipment protection environment, embodiments ofthe invention are operational with numerous other general purpose orspecial purpose equipment protection environments or configurations. Theequipment protection environment is not intended to suggest anylimitation as to the scope of use or functionality of any aspect of theinvention. Moreover, the environment described herein should not beinterpreted as having any dependency or requirement relating to any oneor combination of components illustrated in the exemplary operatingenvironment.

The order of execution or performance of the operations in theembodiments of the invention illustrated and described herein is notessential, unless otherwise specified. That is, the operations may beperformed in any order, unless otherwise specified, and embodiments ofthe invention may include additional or fewer operations than thosedisclosed herein. For example, it is contemplated that executing orperforming a particular operation before, contemporaneously with, orafter another operation is within the scope of aspects of the invention.

When introducing elements of aspects of the invention or embodimentsthereof, the articles “a,” “an,” “the,” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising,”including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

1. A circuit interruption device comprising: a conductive elementconfigured to be coupled to a circuit; a contact arm configured to movewith respect to said conductive element between a first position and asecond position; and a biasing element configured to apply a biasingforce on said contact arm to maintain contact between said contact armand said conductive element when said contact arm is in the firstposition, said contact arm configured such that a current flow throughsaid contact arm causes an electromagnetic repulsive force to act onsaid contact arm in a second direction that is opposite the firstdirection.
 2. A circuit interruption device in accordance with claim 1,wherein said contact arm comprises a first portion, a second portion,and a third portion, said third portion between said first portion andsaid second portion.
 3. A circuit interruption device in accordance withclaim 2, wherein the current flow through said second portion causes therepulsive force as the current flow exits said second portion and enterssaid conductive element.
 4. A circuit interruption device in accordancewith claim 2, wherein said third portion has a width less than a widthof said first portion and a width of said second portion.
 5. A circuitinterruption device in accordance with claim 2, wherein at least aportion of said third portion comprises a nonconductive material.
 6. Acircuit interruption device in accordance with claim 1, wherein when thecurrent flow has a predetermined amplitude, the repulsive force causedby the current flow overcomes the biasing force to cause said contactarm to move in the second direction from the first position to thesecond position.
 7. A circuit interruption device in accordance withclaim 1, wherein said conductive element comprises a first electricalcontact and said contact arm comprises a second electrical contact, saidbiasing element configured to apply the biasing force to said contactarm in the first direction to maintain contact between said firstelectrical contact and said second electrical contact when said contactarm is in the first position.
 8. A circuit interruption device inaccordance with claim 7, wherein the current flow through said contactarm causes the repulsive force in the second direction as the currentflow exits said second electrical contact and enters said firstelectrical contact.
 9. A circuit interruption device in accordance withclaim 1, further comprising at least one arc mitigation plate positionedabove at least a portion of said conductive element, said at least onearc mitigation plate configured to extinguish an arc created by aseparation of said contact arm from said conductive element caused bythe repulsive force.
 10. A trip mechanism for use with a circuitbreaker, said trip mechanism comprising: a conductive element configuredto be coupled to a circuit; and a contact arm configured to move withrespect to said conductive element in a first direction and a seconddirection that is opposite the first direction, said contact armconfigured such that a current flow through said contact arm causes anelectromagnetic repulsive force to act on said contact arm in the seconddirection.
 11. A trip mechanism in accordance with claim 10, whereinsaid contact arm comprises a first portion, a second portion, and athird portion, said third portion between said first portion and saidsecond portion.
 12. A trip mechanism in accordance with claim 11,wherein the current flow through said second portion causes therepulsive force as the current flow exits said second portion and enterssaid conductive element.
 13. A trip mechanism in accordance with claim11, wherein said third portion has a width less than a width of saidfirst portion and a width of said second portion.
 14. A trip mechanismin accordance with claim 11, wherein at least a portion of said thirdportion comprises a nonconductive material.
 15. A trip mechanism inaccordance with claim 11, wherein when the current flow has apredetermined amplitude, the repulsive force caused by the current flowovercomes the biasing force to cause said contact arm to move in thesecond direction from the first position to the second position.
 16. Amethod of assembling a circuit breaker, comprising: coupling aconductive element to a circuit; positioning a contact arm with respectto the conductive element; and coupling a biasing element to the contactarm, the biasing element configured to apply a biasing force on thecontact arm in a first direction to maintain contact between the contactarm and the conductive element when the contact arm is in the firstposition, the contact arm configured such that a current flow throughthe contact arm causes an electromagnetic repulsive force to act on thecontact arm in a second direction that is opposite the first direction.17. A method in accordance with claim 16, further comprising defining anelectrical path such that, when the current flow is greater than apredetermined amplitude, the repulsive force caused by the current flowovercomes the biasing force to cause the contact arm to move in thesecond direction from the first position to the second position.
 18. Amethod in accordance with claim 16, further comprising positioning atleast one arc mitigation plate above at least a portion of theconductive element, the at least one arc mitigation plate configured toextinguish an arc created by a separation of the contact arm from theconductive element when the contact arm moves from the first position tothe second position.
 19. A method in accordance with claim 16, furthercomprising providing the contact arm, wherein the contact arm includes afirst portion, a second portion, and a third portion between the firstportion and the second portion, the current flow through the secondportion causes the repulsive force as the current flow exits the secondportion and enters the conductive element.
 20. A method in accordancewith claim 16, wherein providing the contact arm comprises defining anotch in the second portion.